Lifting clamp



Feb. 27, 196 8 J. RENFROE LIFTING CLAMP 4 SheetsSheet, 1

Filed April 11, 1966 INVENTOR 12' Fill.

Z W M Feb. 27, 1968 J.L.RENFROE 3,370,881 f LIFIING CLAMP Filed April 11, 1966 FIG. 3. I T

4 Sheets-Sheet 2 mflllllllllllllllll 1'" INVENTOR Josh L. Renfroe A ORNEYS Feb. 27, 1968 RENFROE 3,370,831

r LIFTING CLAMP Filed April 11, 1966 4 Sheets-Sheet INVENT OR Josh L. Renfroe ATTdRNEYS Feb. 27, 1968 L, RENFROE' 3,370,881

LIFTING CLAMP Filed April 11, 1966 4 Sheets-Sheet 4 FIG. 2 58 FIG. 6.

INVENT OR Josh L. Repfroe- A ORNEYS Patented Feb. 27, 1968 3,370,881 LIFTING CLAMP Josh L. Renfroe, Jacksonville, Fla, assignor to J. C.

Renfroe & Sons, Inc., Jacksonville, Fla., a corporation of Florida Filed Apr. 11, 1966, Ser. No. 541,596 11 Claims. (Cl. 294-101) ABSTRACT OF THE DISCLOSURE There is disclosed a lifting clamp having a movable gripping jaw, a shackle, a linkage connecting the shackle to the movable jaw and a locking mechanism engageable with the linkage to lock the jaw in either open or closed positions. The locking mechanism has a unitary construction with a handle located outside of the clamp body, an integral connection between the handle and an interior portion of the locking mechanism, and an arcuate slot in the body to receive such connection. Opposed to the movable jaw is a conventional swivel jaw mounted in a support which comprises a pair of plates welded together and constructed to provide advantageous reinforcement for the clamp body.

This invention relates to clamps for lifting articles such as steel plates and more particularly to such clamps having a locking device to retain the clamp jaws in closed position.

The present invention is an improvement of the inventions disclosed in United States Patent 2,654,630 and Raymond L. Renfroe application Ser. No. 381,193, filed July 8, 1964, now Patent No. 3,297,394, entitled Lifting Clamp.

Patent No. 2,654,630 discloses a clamp comprising a clamp body having a slot to receive an article to be lifted. A pair of jaws are provided on opposite sides of the slot. One of the jaws is movable between open and closed positions relative to the other jaw which is preferably fixed. The movable jaw is operated by a shackle connected to the movable jaw by force multiplying linkage.

The clamp body includes a pair of spaced side plates. Mounted on the inside of one of the side plates and parallel thereto is a pivotal locking plate operated by a handle lever located outside of such side plate. A heavy tension spring connects the locking plate to the linkage which extends between the shackle and the movable jaw. By rotation of the locking lever handle to a closed position the spring exerts a heavy closing force on the movable jaw. At the same time, however, the spring tends to cant the pivot pinconnecting the locking plate to the handle to a position inclined relative to its normal axis. This causes a binding action which makes the lever difficult to operate.

The Raymond Renfroe application Ser. No. 381,193 discloses a clamp having a modified locking mechanism to eliminate the binding action mentioned above. As discussed in that application, however, the modified locking mechanism gave rise to assembly problems. The present invention is directed to an improvement wherein the nonbinding advantages of the Raymond Renfroe clamp are achieved with a simpler, more easily assembled, more dependable structure.

An object of the present invention is to provide an improved lifting clamp of the general type disclosed in Renfroe Patent 2,654,630 having an easily operated lock ree from binding and more particularly such a lock having a simple unitary construction and which is highly dependable, and may be easily assembled into and disassembled from the clamp body.

Another object of the invention is to provide such a clamp having an improved body reinforcing structure.

enerally the invention relates to a lifting clamp which comprises a clamp body including a pair of spaced side plates, said body defining a slot through said side plates to receive an article to be lifted; a pair of opposed jaws mounted on opposite sides of said slot, one of said jaws being pivotally mounted for opening and closing movement relative to the other jaw; a shackle mounted for guided movement in said clamp body and adapted for connection to a lifting force; link means connecting said shackle to said movable jaw to close said movable jaw when a lifting force is applied to said shackle, said link means and said movable jaw forming an assembly; locking means comprising a pair of spaced locking plate members pivotally connected to said side plates for rotation about an axis transverse to said side plates, a cross member eccentric with said axis connecting said plate members together at opposing positions adjacent said side plates, a spring connecting said cross member to said assembly, a manually operated handle pivotally connected outside of said clamp body for rotation about said axis, and a connecting bar extending through one of said side plates along a line eccentric with said axis to non-rotatably connect said handle to one of said plate members so that rotation of said handle causes corresponding rotation of said plate members to move said locking means between a closed position where said spring exerts a jaw closing force on said assembly and an open position where said spring permits said movable jaw to remain open, said one side plate having an arcuate slot to accommodate said connecting bar during said rotation of said plate members; and stop means to retain said locking means in closed position. In addition the clamp has an improved body reinforcing structure which may be employed with or without the improved locking device.

The invention having been generally described, a preferred specific embodiment will now be set forth in detail with reference to the accompanying drawings in which:

FIGURE 1 is a front elevation of a clamp according to the present invention;

FIGURE 2 is a left side elevation of the same clamp;

FIGURE 3 is a sectional view taken along the line 33 of FIGURE 2 showing the movable jaw in a closed position, its operating linkage and the lock mechanism;

FIGURE 4 is a sectional view similar to FIGURE 3 showing the movable jaw in a locked open position;

FIGURE 5 is a right side elevation;

FIGURE 6 is a sectional view taken along the line 6-6 of FIGURE 3;

FIGURE 7 is an exploded view of the locking mechamsm; and

FIGURE 8 is a sectional view taken along the line 83 of FIGURE 1.

With reference to the drawings, the invention includes a clamp body 11 which includes a pair of side plates 12 and 13. Preferably the side plates are permanently connected together by an elongated cross bar 14, the lower end of which extends to a position close to but slightly spaced from the bottom edge of the side plates 12 and 13 as best shown in FIGURE 3. The upper end of the cross bar 14 extends nearly to the top of the side plates 12 and 13. The cross bar 14 is permanently welded in place to provide a rigid and strong reinforcing for the clamp body. The termination of the bottom end of the cross bar 14 at a position slightly spaced from the lower edges of the side plates 12 and 13 facilitates the welding operation. With such spacing a fillet weld 15 may be placed along each corner of the bottom edge of the bar 14. If the bar 1-4 is flush with the bottom edge of the clamp body it would be necessary to bevel the ends of the bar to provide a weld along the corners of the bottom edge.

The side plates 12 and 13 are also connected together by a strut 16 which consists of a cylindrical sleeve 17 connected as a spacer between the side plates by a bolt 18, having a head 19 outside of the side plate 12.

The clamp body 11 defines a vertical slot 23 which extends through both of the side plates 12 and 13 to receive an article to be lifted. The clamp is particularly adapted for the lifting of heavy steel plates used in the construe tion industry, it being understood that many other different articles can be handled. Mounted on opposite sides of the slot 23 are a pair of jaws 24 and 25. The jaw 24 is fixed against axial movement and the jaw 25 is movable as later described.

The jaw 24 is a conventional swivel jaw which is freely pivotable about its own axis around a connecting bolt 26 which is connected through an opening in the bar 14 and retains the jaw 24 against axial movement. The jaw 24 has a sharpened protruding ridge 27 (FIGURE 6) which grips the article being lifted.

Welded in face-to-face relation to the inner surface of the bar 14 is a face plate 28, having a circular opening 29 closely surrounding and corresponding to the circular periphery of the swivel jaw 24. As seen in FIG- URE 6 the face plate 28 is T -shaped with a narrow upper portion 31 extending above the slot 23 between the side plates 12 and 13. Just above the top of the swivel jaw 27 the face plate 28 broadens out and extends to the extreme front and rear faces of the clamp body 11 to define a broad base portion 32.

The use of the separate face plate and backing bar 14 rather than a single bar eliminatesthe necessity for a counterbore in such bar to receive the swivel jaw 24. Time consuming machining operations are thus elirninated.

The movable jaw 25 is pivoted about a removable pin 35 which extends through the side plates 12 and 13. The jaw 25 has an arcuate gripping face with a plurality of sharpened teeth 26 which bite into the article being lifted.

Movable jaw 25 is also connected by a pin 37 to the lower end of an elongated link means 38, the upper end of which is connected by a pivot pin 39 to the lower end of a shackle 41. The link means 38 comprises a pair of spaced flat link bars 42 and 43.

The shackle pin 39 extends through both of the bars 42 and 43 and into a pair of opposed vertical slots 44 and 45 in the interior surface of the side plates 12 and 13. The shackle 41 is movable vertically in the clamp body by the sliding action of the pin 39 in the slots 44 and 45. The slots limit the non-rotational movement of the pin 39 to a vertical path. The shackle at its upper end has a lifting connection formed by a large opening 46 adapted to receive a conventional lifting hook at the end of a hoisting cable.

When the clamp is mounted on a plate which is in a horizontal position with the movable jaw on top'of the plate, application of lifting force to the opening 46 causes the shackle to pivot and engage the sleeve 17 which serves as a fulcrum thereby causing the shackle to raise the pin 39 in the slots 44 and 45 and applying a closing force to the jaw 25 in the manner fully described in Patent 2,654,630. When a force is applied to the opening 46 in the shackle 41 in a horizontal (relative to the vertical slot 23) direction toward the 'swivel jaw 24, the shackle engages the top of the bar 14 which serves as a fulcrum causing the pin 39 to be raised and the jaw 25 to be closed.

Thus the elongated bar 14 functions both to reinforce the clamp body and to serve as a fulcrum for the shackle 41. The upward extension of the bar above the uppermost position of the movement of the shackle pin reinforces the clamp body and minimizes the chance of failure of the side plates along a line extending diagonally upward and across the bar 14 from the top of the slot 23. This construction enables the lateral width of the clamp body on the swivel jaw side of the slot 23 to be substantially less than in prior art clamps. The present clamp thus can be used in places which would be inaccessible to prior art clamps.

As shown in FIGURES 3 and 4, the shackle may be moved between an elevated position as shown in FIG- URE 3, and a depressed position as shown in FIGURE 4,

in which the movable jaw 25 is closed and opened respectively. As also shown in these figures the lower corner 51 of each of the side plates 12 and 13 covers the assembly composed of movable jaw 25 and the link means 38 during the entire path of movement of such assembly except that the gripping portion of the movable jaw is exposed in the slot 23.

An important feature of the present invention is its improved locking mechanism. Such mechanism includes a pair of locking plate members 52 and 53 connected together by a cross member 54 which is welded or otherwise permanently connected between the plate members.

' Non-rotatably connected to the plate member 52 is a handle 56 as shown in FIGURE 7. The non-rotatable connection is provided by a connecting bar 57 which is preferably integral with both the plate member 52 and the handle 56. Thus the two plate members 52 and 53 and the handle 56 preferably comprise an integral one piece locking assembly 50. The locking assembly 50 is connected to the clamp body 11 by a pair of pivot bolts 58 and 59, having circular heads 61 and 62 which are received within corresponding openings 63 and 64 in the plate members 52 and 53.

A primary advantage of the novel structure of the locking mechanism is its solid unitary construction coupled with the facility with which it may be assembled into the clamp body 11. The plate members 52 and 53 are slipped between the interior faces of the side plates 12 and 13 of the clamp body 11. The handle 56 fits outside of the side plate 12. The connecting bar 57 moves through an opening 65 (FIGURE 1) in the side plate 13 into an arcuate slot 66. The side plates 12 and 13 are bored to receive the pivot bolts 58 and 59, which are slipped through the openings 62 and 64 respectively outwardly from the space between the plate members 52 and 53 until the shoulders inside of the heads 61 and 62 abut the interior faces of the side plates 12 and 13. A sleeve 71 is mounted around the pivot bolt 58 inside of the handle 56 as best shown in FIG- URE 8. The sleeve 71 is slightly longer than the thickness of the handle 71 so that a nut 72 may be tightened against the sleeve which then transmitsthe force between the nut and the side plate 12 without binding the handle 56 which is thus free to rotate about the sleeve 71 as a pivot. A nut 73 is connected to the pivot bolt 59 and the locking assembly 50 is secured in its position. A heavy tension spring 75 is connected between the cross members 54 and a pin 76 which extends between link bars 42 and 43 of link means 38.

It is desirable to keep the interior faces of the plate members 52 and 53 free of protrusions at the pivots to leave the space between such faces clear for the operation of the tension spring 75. Thus the bolt heads 61 and 62 are flush with the interior faces of the plate members 52 and 53. v

Manual rotation of the handle 56 causes rotation of the locking plate members 52 and 53 about the axis of the pivots 58 and 59. The cross member 54 and the connecting bar 57 are both eccentric with such axis. When the handle 56 is rotated to a closed position as shown in phantom lines in FIGURE 3 the locking plate members 52 and 53 assume the position shown. The locking device is held in locked position by an overcenter mechanism. In the closed or locked position the tension spring 75 exerts a closing force on the assembly of the link means 38 and the movable jaw 25. In this position the axis of the spring 75 is inside of the pivot 58. Further rotation of the locking plate members is prevented by engagement of the handle 56 with the head.

19 of the nut 18. Moreover, a protruding pawl 82 on the plate member 52. engages the sleeve 17 which also functions as a stop member.

When the handle 56 is rotated in a clockwise direction as shown in FIGURES 1 and 3 until the axis of the spring 75 passes to the outside of the pivot 58 the spring then pulls the handle down toward the open position shown in phantom lines in FIGURE 4. In that position the spring exerts no closing force on the movable jaw 25 which is permitted to remain fully open.

The protruding pawl 82 of the locking plate member 52 when the lock is in the open position engages an upwardly facing shoulder 83 on the link bar 42 to lock the clamp in the open position. If desired in .heavier clamps a pawl 71 may be mounted on each of the locking plate members 52 and 53 to engage both of the link bars 42 and 43.

During the rotation of the handle 56 back and forth between the open and closed positions the connecting bar 57 moves freely in the arcuate slot 66.

The general operation of the clamp is the same as that more fully described in Patent 2,654,630.

There has been illustrated and described what is considered to be a preferred embodiment of the invention. It will be understood, however, that various modifications may be made by persons skilled in the art without departing from the scope of the invention which is defined solely by the appended claims.

What is claimed is:

1. A lifting clamp which comprises a clamp body including a pair of spaced side plates, said body defining a slot through said side plates to receive an article to be lifted;

a pair of opposed jaws mounted on opposite sides of said slot, one of said jaws being pivotally mounted for opening and closing movement relative to the other jaw;

a shackle mounted for guided movement in said clamp body and adapted for connection to a lifting force;

link means connecting said shackle to said movable jaw to close said movable jaw when a lifting force is applied to said shackle, said link means and said movable jaw forming an assembly;

locking means comprising a pair of spaced locking plate members pivotally connected to said side plates for rotation about an axis transverse to said side plates,

a cross member eccentric with said axis connecting said plate members together at opposing positions adjacent said side plates,

a spring connecting said cross member to said as sembly,

a manually operated handle pivotally connected outside of said clamp body for rotation about said axis, and

a connecting bar extending through one of said side plates along a line eccentric with said axis to non-rotatably connect said handle to one of said plate members so that rotation of said handle causes corresponding rotation of said plate members to move said locking means between a closed position where said spring exerts a jaw closing force on said assembly and an open position where said spring permits said movable jaw to remain open,

said one side plate having an arcuate slot to accommodate said connecting bar during said rotation of said plate members; and

stop means to retain said locking means in closed position.

2. A lifting clamp according to claim 1 wherein said connecting bar is integral with said one plate member and said one side plate has an opening between said slot and an edge of said one side plate to admit said connecting bar.

3. A lifting clamp according to claim 2 wherein said cross member is integral with said plate members and said connecting bar is integral with both said one plate member and said handle.

4. A lifting clamp according to claim 3 wherein said plate members are connected at said axis to said side plates by threaded fastenings having circular heads which serve as pivots for said plate members, said heads havin g shoulders abutting the interior faces of said side plates, one of said fastenings extending through said handle and having a cylindrical sleeve surrounding said one fastening and extending through said handle to serve as a pivot for said handle, said sleeve being longer than the thickness of said handle to transmit force between a nut on the outer end of said one threaded fastening and said one side plate while preventing binding between said nut and said handle.

5. An apparatus according to claim 1 further comprising a generally vertical reinforcing bar connecting said side plates on one side of said slot,

said other jaw comprising a swivel jaw rotatably connected to said bar and having a gripping surface with a sharp protrusion facing into said slot, said swivel jaw having a circular periphery and being restrained against axial movement transverse to said slot,

at face plate welded in face-to-face relation to said bar and having a circular opening closely surrounding and corresponding to the circular periphery of the said swivel jaw,

said shackle being connected to said link means by a pivot,

means in said clamp body to limit the non-rotational movement of said pivot to a vertical path,

said bar extending from a position below said jaws near the bottom of said side plates to a position above the top of the path of movement of said pivot near the tops of said side plates thereby reinforcing said side plates and minimizing the width thereof on said one side of said slot, and

stop means spaced on the opposite side of said shackle from said bar so that said stop means and the top of said bar define fulcrums engageable by said shackle when a horizontal force is applied to the top of said shackle thereby raising said pivot along said vertical path.

6. A lifting clamp which comprises a clamp body including a pair of spaced side plates, said body defining a generally vertical slot through said side plates to receive an article to be lifted,

a generally vertical reinforcing bar connecting said side plates on one side of said slot,

a swivel jaw rotatably connected to said bar and having a gripping surface with a sharp protrusion facing into said slot, said swivel jaw having a circular periphery and being restrained against axial movement transverse to said slot, said swivel jaw having a flat base surface opposite said gripping surface, said bar having a bearing surface engaging said flat base surface,

a face plate welded in face-to-face engagement with said bar and having a circular opening closely surrounding and corresponding to the circular periphery of said swivel jaw, the engagement of said face plate with said bar being in the same plane as the engagement of said fiat base with said bearing surface,

a movable jaw pivotally mounted across said slot from and facing said swivel jaw for opening and closing movement relative to said swivel jaw,

a shackle mounted for guided movement in said clamp body and adapted for connection to a lifting force,

link means connecting said shackle to said movable jaw to close said movable jaw when a lifting force is applied to said shackle, said link means and said movable jaw forming an assembly, and

locking means connected to said assembly to apply a resilient closing force to said movable jaw.

7. A lifting clamp according to claim 6 wherein the lower end of said bar terminates at a position close to but slightly spaced from the adjoining lower ends of said side plates and is welded thereto, said face plate having its lower end extending beyond the lower end of said bar and welded thereto.

8. A lifting clamp according to claim 6 wherein said bar extends upwardly to a position near the tops of said side plates thereby reinforcing said side plates and minimizing the width of said side plates on said one side of said slot.

9. A lifting clamp according to claim 8 wherein said shackle is connected to said link means by a pivot and further comprising means in said clamp body to limit the non-rotational movement of said pivot to a vertical path, stop means spaced on the opposite side of said shackle from said bar so that said stop means and the top of said bar define fulcrums engageable by said shackle when a horizontal force is applied to the top of said shackle thereby raising said pivot along said vertical path.

10. A lifting clamp which comprises a clamp body including a pair of spaced side plates,

said body defining a generally vertical slot through said side plates to receive an article to be lifted,

a generally vertical bar connecting said side plates on one side of said slot,

a pair of opposed jaws mounted on opposite sides of said slot, one of said jaws being pivotally mounted for opening and closing movement relating to the other jaw,

a shackle mounted for guided movement in said clamp body and adapted for connection to a lifting force,

link means connecting said shackle to said movable jaw to close said movable jaw when a lifting force is applied to said shackle, said link means and said movable jaw forming an assembly, 7

locking means connected to said assembly to apply a resilient closing force to said movable jaw,

said shackle :being connected to said link means by a pivot,

means to limit the non-rotational movement of said pivot to a vertical path, said bar extending from a position below said jaws near the bottom of said side plates to a position above the path of movement of said pivot near the tops of said side plates thereby reinforcing said side plates and minimizing the .Width thereof on one side of said slot, and

stop means spaced on the opposite side of said shackle from said bar so that said stop means and the top of said bar define fulcrums engageable by said shackle when a horizontal force is applied to the top of said shackle thereby raising said pivot along said vertical path.

11. A lifting clamp according to claim 10 wherein the lower end of said bar terminates at a position close to but slightly spaced from the adjoining lower ends of said side plates and is welded thereto.

References Cited UNITED STATES PATENTS 2,654,630 10/1953 Renfroe 294-104 GERALD M. FORLENZA, Primary Examiner.

G. F. ABRAHAM, Assistant Examiner. 

